Most tastants and odorants are identified through a composite of responses from non-specific interactions. The pattern created by the simultaneous response of a series of receptors is specific for a particular set of stimuli. A device that mimics the mammalian sense of taste was recently developed at U.T. by using arrays of resin beads that are chemically derivatized with molecular sensors, placed into a micromachined platform. The spectroscopic pattern from all the beads in the array was found to be specific for a particular mixture of analytes. To take this technology to the next stage, there is a need to develop strategies for achieving optical responses from beads when receptors for different classes of analytes are attached. This proposal entails studies aimed at addressing two areas. First, we propose to test the efficiency of indicator displacement assays for optical signaling. Indicators responsive to pH effects and Ca(ll) binding will be used to signal analyte binding. Second, we intend to explore the ability to use differential receptors to fingerprint the components present in a complex mixture of analytes. These two goals will be explored within the context of two highly challenging complex solutions: wine and urine. The reason for the choice of wine and urine as our test-bed solutions is due to their complexity and the uniquely similar chemical structures. We propose to target five classes of analytes: carboxylic acids, sugars, pectins, tannins, and gluoconorides. These classes present different challenges for fingerprinting. We will use """"""""in-hand"""""""" receptors for carboxylates, sugars and gluconorides. Alternatively, the receptors for the pectins, tannins and gluconorides will be derived from combinatorial chemistry. In practice, synthetic receptors suffer interference from similar analytes due to their simplicity. Yet, we feel that the power of an array of synthetic receptors, when coupled with pattern recognition protocols, cannot be exceeded for array sensor applications. Synthetic receptors are naturally cross-reactive, the exact attribute that is desired in an array setting. Furthermore, the use of synthetic combinatorial chemistry in the creation of unnatural receptors naturally compliments this requirement of cross reactivity. Our goal is to teach this general lesson to the supramolecular and analytical chemistry community.
